1. Field of the Invention
The present invention relates to a tape reel and a take-up reel on which is wound a recording tape, such as a magnetic tape or the like, which is used as a recording/playback medium mainly of computers or the like, and to a recording tape cartridge which accommodates the tape reel within a case, to a pullout member which pulls out the recording tape from the recording tape cartridge and is accommodated in the take-up reel, and to a drive device which is provided with the take-up reel and into which the recording tape cartridge is loaded.
2. Description of the Related Art
There are conventionally known recording tape cartridges in which a recording tape, such as a magnetic tape or the like which is used as a data recording/playback medium (for data backup) of computers or the like, is wound on the hub (core portion) of a reel (tape reel), and the reel is singly accommodated within a case. When the recording tape cartridge is loaded into a drive device, the recording tape is pulled out via a leader member from an opening provided in the recording tape cartridge. The pulled out recording tape is, via tape guides and a recording/playback head, taken-up onto a take-up reel within the drive device.
In the recording tape cartridge of this configuration, an increase in the recording capacity of the recording tape is always desired. The main factors supporting the increase in the recording capacity of the recording tape include: (1) improving recording density (improving linear recording density, improving track density); (2) increasing recording area (increasing the tape length by thinning the recording tape); (3) improving servo tracking control; and (4) increasing the traveling speed of the recording tape.
However, there are the following problems in the aforementioned (1) to (4), and solutions for those problems are continuously sought after. In particular, ensuring that tape edge damage with respect to an impact when the recording tape cartridge is dropped or the like when the recording tape cartridge is not in use (during transport, during handling) can be reduced and ensuring that tape edge damage during travel of the recording tape when the recording tape cartridge is in use (when the recording tape cartridge has been loaded into a drive device) are sought after.
(1) When recording density improves, the recording size of the data signal also becomes smaller, and the allowable amount of fluctuation in the width direction of the recording tape during travel inside the drive device, and particularly fluctuation at a high frequency (fluctuation in a short amount of time), becomes smaller. That is, when the recording tape fluctuates significantly in its width direction during travel, the recording/playback head that moves in the width direction of the recording tape on the basis of servo signals on the recording tape becomes unable to follow a sudden fluctuation in the position of the recording tape, errors in reading servo signals occur, and it becomes unable to record and play back the desired data signal.
(2) When the recording tape is thinned, the edge strength of the recording tape drops and it becomes easier for the recording tape to sustain tape edge damage. That is, when the recording tape cartridge sustains an impact during transport or as a result of the recording tape cartridge being dropped or the like, it becomes easier for the edge of the recording tape protruding from the wound surface of the reel to hit flanges and bend. Further, due to thinning of the recording tape, the allowable stress of the recording tape with respect to pressure applied to the recording tape drops when the recording tape is wound on the reel or when the recording tape is stored over a long period of time.
(3) When the size of the servo signal becomes smaller or the recording density of the servo signal itself improves and servo tracking control improves, the allowable amount of fluctuation in the width direction of the recording tape during travel inside the drive device, and particularly fluctuation at a high frequency (fluctuation in a short amount of time), becomes smaller. That is, when the recording tape fluctuates significantly in its width direction during travel, the recording/playback head that moves in the width direction of the recording tape on the basis of servo signals on the recording tape becomes unable to follow a sudden fluctuation in the position of the recording tape, errors in reading servo signals occur, and it becomes unable to record and play back the desired data signal.
When the traveling speed of the recording tape is increased, there is no longer leeway with respect to the response speed of servo tracking control. Further, there is the potential to induce high-frequency vibration. Further, the impact force when the edge of the recording tape contacts flanges of a take-up reel or tape guides of the drive device and moreover flanges of the reel of the recording tape cartridge becomes greater, which becomes disadvantageous to recording tape that has been tinned and whose edge has become weaker.
It is commonly understood that the rigidity of recording tape is affected in cube by a reduction in its thickness. For example, when the thickness of the recording tape is from 8.9 μm to 6.6 μm, it is 6.63÷8.933=0.41 with respect to 6.6÷8.9=0.74, and when the thickness is reduced 26%, the rigidity is reduced 59%. There is a tendency for recent recording tape to be thinned in order to increase recording capacity per one recording tape cartridge, and there is concern for a drop in rigidity, that is, a drop in edge strength, and susceptibility to plastic deformation.
Further, as described in Japanese Patent Application Laid-Open (JP-A) No. 2005-251283, for example, it has conventionally been disclosed that the wound shape (wound surface) is regulated (regulated windability is improved) in a reel where, as the recording tape is wound on the reel, the hub diameter on one end side of the outer peripheral surface of the hub becomes smaller with respect to the hub diameter on the other end side. However, when a difference in diameter is given to both end portions of the hub and the recording tape is set toward one side, there is the potential for the recording tape to be excessively set toward one flange side due to a combination with the curvature (curvature in the width direction) of the recording tape, whereby there is the potential for the edge of the recording tape to strongly contact flanges or tape guides of the drive device (the potential for tape edge damage to occur).
Further, as described in JP-A No. 6-309837, for example, causing the width direction central portion of the hub to swell (in a convex shape) into a substantially barrel shape in a reel or the like on which recording tape is wound has conventionally been disclosed. In this JP-A No. 6-309837, a helical scan rotating head is disclosed. In this rotating head, the contact angle/contact area with the recording tape is large and the traveling speed of the recording tape is also slow, so control of the width direction position of the recording tape is relatively easy in comparison to a linear recording fixed head, and it is relatively easy to control by the travel system of the drive device.
However, in a rotating head where the contact angle is large and the head is slanted, there is the problem that when it is loaded into a rotating drum, the edge of the recording tape catches on the head and damage occurs to the recording tape. In order to solve this, in JP-A No. 6-309837, correcting the value of the cupping amount in a negative direction when cupping of the recording tape is large (in this JP-A No. 6-309837, when cupping is positive) is disclosed.
That is, large positive cupping of the recording tape is corrected to a small positive, ±0, slightly negative by a substantially barrel-shaped hub. Thus, a situation where the edge of the recording tape catches on the rotating head and damage occurs to the recording tape is prevented, and alignment with respect to the head is improved.
However, when the recording tape is thinned, with the large swelling amount of the barrel shape disclosed in JP-A No. 6-309837, deformation in an undulating shape and cinching occur in the tape edge (though this is not expressly stated in JP-A No. 6-309937). According to an experiment by the present applicant, the swelling amount of the barrel shape of the occurrence boundary thereof was around 0.08 mm when recording tape having a thickness of 6.6 μm, for example, was wound on a hub having a wall thickness of 2.5 μm and made of 10% glass fiber-reinforced PC resin. That is, when it becomes larger than this, deformation in an undulating shape and cinching would occur.